The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have developed an improved and excellent video compression technology, compared to existing MPEG-4 Part 2 and H.263 standards. The new standard is called H.264/AVC (Advanced Video Coding) and was released jointly as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264. The H.264/AVC (hereinafter referred to as ‘H.264’) uses a spatial predictive coding method, which is different from known international video coding standards such as MPEG-1, MPEG-2, MPEG-4 Part2 Visual and the like. Known video coding methods use “intra prediction” for coefficients transformed in discrete cosine transform (DCT) domain to seek higher encoding efficiency, resulting in degradation of the subjective video quality at low band transmission bit rates.
However, the inventor(s) has noted that H.264 adopts an encoding method based on a spatial intra prediction in a spatial domain rather than in a transform domain. An encoder using an encoding method based on the known spatial intra prediction predicts a block to be currently encoded based on information about a previous block that has been encoded and reproduced, and encodes only information about difference from an actual block to be encoded to transmit the encoded information to a decoder. In this case, to be able to predict the block, the decoder is provided with a transmission of parameters necessary for block prediction, or it shares parameters necessary for prediction through synchronization with the encoder. The decoder generates and reproduces a desired block to be currently decoded by predicting a target block using a decoded neighboring block and adding difference information transmitted from the encoder to the predicted target block. If parameters necessary for prediction have been transmitted from the encoder, the decoder uses the parameters to predict the target block.
The inventor(s) has, however, noted that when prediction is performed by using intra prediction according to a known video encoding method or video decoding method, pixels of a target block are predicted by using reconstructed adjacent pixels located in a neighboring block (mainly, the left and upper blocks of the target block) adjacent to the block to be currently encoded. In a case where the prediction is performed using existing adjacent pixels because many quantization errors exist or complexity is high in a certain region according to characteristics of images, the inventor(s) has experienced that there may exist a region where the prediction is not well performed. The inventor(s) has noted that in such a region, prediction may not be well performed with a known intra encoding. The inventor(s) has experienced that the reduced prediction accuracy increases a difference between a pixel value of an original pixel and a predicted pixel value, lowering compression efficiency.